Cardiovascular autonomic control during application of different modes of noninvasive ventilation in patients affected by amyotrophic lateral sclerosis

Background: Cardiovascular events commonly cause death in amyotrophic lateral sclerosis (ALS) even in patients treated by noninvasive ventilation (NIV). Objectives: to evaluate autonomic function with the assessment of heart rate variability (HRV) in ALS patients treated by assist pressure control ventilation (APCV) and assist control ventilation (ACV) during sleep. Methods: Consecutive ALS patients underwent one polysomnography during APCV and one during ACV. HRV was analyzed both in the total sleep period (from first stage N1 to last awakening) and in a 5-minute period of stable stage N2. Time domain, frequency domain and nonlinear indexes of HRV were measured. Results: Nineteen patients (age 62.0 ± 8.7, 9F/10 M) were studied. The analysis did not reveal differences in blood gasses between NIV modalities, but a longer expiratory time (3.01±0.6 vs 2.8 ± 0.6 s, respectively APCV vs ACV, p = 0.001) and a lower arousal index (17.5 ± 9.1 vs 23.1 ± 13.9, p = 0.02) during APCV. HRV was indicative of higher vagal activity during APCV, especially in the 5-minute periods. In the total sleep periods, the HRV time domain indexes reflecting parasympathetic activity were positively correlated with the expiratory time and negatively with the inspiratory/expiratory time ratio. Low frequencies were positively, and high frequencies negatively, correlated with inspiratory time. HRV and sleep structure parameters were not correlated, except very low frequencies that were correlated to the arousal index. Conclusions: Respiratory influences on autonomic control can be preserved in ALS. The slower breathing pattern during APCV may help to maintain a higher vagal activity. Through this mechanism, in the long-term APCV could more beneficial to ALS patients than ACV.